Polar Code Bit Freezing for Puncturing-Induced Reliability Loss
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Solution Overview
Problem
In mobile communications based on 3GPP standards for 5G New Radio (NR) control channels, polar codes face issues with subblock interleaving and rate-matching, leading to vulnerable input bits and degradation of code block error performance due to puncturing and shortening, which negatively impact polarization effects.
Innovation Solution
Implementing additional bit freezing techniques for polar coding, including freezing specific subblocks or bit positions to mitigate vulnerabilities, such as freezing the least indexed subblock when its size is less than a threshold, setting information bits to zero for chase-combining HARQ, and freezing the smallest N/2 bit positions when the number of punctured bits exceeds N/2, to preserve system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rate-matching and subblock interleaving are applied to polar codes, then code flexibility and transmission efficiency are improved, but input bits become vulnerable to errors and code block error performance degrades
Solution Approach 1:
The patent applies preliminary action by freezing specific input bits before the rate-matching and interleaving processes. By pre-determining which bits to freeze based on their vulnerability to puncturing and shortening, the system prepares the code structure in advance to withstand the subsequent rate-matching operations, thereby maintaining reliability while preserving transmission efficiency.
Solution Approach 2:
The patent implements local quality by applying different freezing strategies to different portions of the input bit sequence. Specifically, it freezes the least indexed subblock when its size is below a threshold, and freezes the smallest N/2 bit positions when punctured bits exceed N/2. This localized approach targets vulnerable regions without unnecessarily constraining the entire code block, thus balancing reliability and productivity.
2Adaptability or versatility
If puncturing and shortening are used in rate-matching, then transmission adaptability is improved, but polarization effect on input bits is negatively impacted
Solution Approach 1:
The patent applies preliminary anti-action by counteracting the negative effects of puncturing and shortening before they occur. By freezing vulnerable input bits in advance, the system preemptively protects against the polarization degradation that would otherwise result from rate-matching operations, thereby maintaining transmission adaptability while preserving the polarization effect.
Solution Approach 2:
The patent implements local quality by selectively freezing bits based on their specific vulnerability to puncturing and shortening. The freezing strategy adapts locally to the rate-matching conditions: freezing the least indexed subblock when small, and freezing the smallest N/2 positions when heavily punctured. This localized protection maintains polarization effects in non-vulnerable regions while allowing adaptability in punctured regions.
Data Source
AI summary
Examples pertaining to additional bit freezing for polar coding are described. An apparatus performs polar coding to encode a plurality of input subblocks of information bits, frozen bits and optional cyclic redundancy check (CRC) bits to generate a plurality of subblocks of coded bits. The apparatus then transmits at least some of the subblocks of coded bits. In performing the polar coding, the apparatus additionally freezes one of the plurality of input subblocks corresponding to one of the interleaved plurality of subblocks of coded bits which decreases polarization gain due to puncturing.